Imultaneous catalytic spectro-photometric determination of nitrite and nitrate in flour and water with flow injection analysis

The nitrate content is an important factor for environmental water samples and flour. In a 0.35 mol/L H₂SO₄ solution, NO₂- has a strong catalyzing function on the decolourization of Gallocyanine (GC) oxidated by NaBrO₃.. Based on this, a novel method was developed to measure the NO₂-and NO₃- concentrations in water and flour. The flow injection technology was introduced into the analysis system. A single-valve dual-cingulums to inject which the Copperized-Cadmium slice and the reduction zone are isolated. The optimum solution for this method contains 1.48×10^-4 mol/L GC, 0.06 mol /L NaBrO₃ and 0.2 mol /L of NH4Cl. Two empirical equations were proposed to calculate the NO₂ - and NO₃- concentrations based on the measured signals. It can be used to measure NO₂- of from 0.001 mg / L to 2.6 and NO₃ - of from 0.002 mg / L to 3.6 mg / L. The measurement frequency can be up to 20 samples / h. The relative standard deviation for eleven samples is less than 5%.